DE2245612A1 - METAL CEMENTING METHOD - Google Patents

Description

The invention relates to cementing processes in which a metal is precipitated from a salt solution by a more electropositive metal which replaces the first-mentioned metal in the solution. The metal used is referred to as the precipitant, the metal obtained is referred to as the precipitation product. According to a preferred embodiment, the invention relates to the use of pig iron as a precipitating agent under conditions under which yields as high as 93.9% of the achievable precipitate in the form of cemented metal of very high purity are obtained.

In the method of the invention, a metal, such as copper, is cemented onto a precipitant in Form of a more electropositive metal, such as iron, from a

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ORIGINAL INSPECTED

acidic saline solution. The method is characterized by daö one the precipitant in the form of a grain size graded mixture of particles with a high surface area / volume ratio but of sufficient size to ensure self-abrasion under stirring or agitation conditions, and the precipitant begins constantly in an amount corresponding to the several hundred to several thousand times the amount stoichiametri & ch to fill of the desired metal required from the solution.

The extraction of copper from leaching solutions by Precipitation on iron has been known for hundreds of years. The chemical reaction for copper sulfate is as follows:

Fe + CuSO ₄ > Cu + FeSO. , (1)

On a stoichiometric basis, this conversion consumes 0.8.8 kg Iron per kg of copper produced. However, the solutions are acidic and more iron is consumed after the following reactions:

Fe + Fe ₂ (SO ₄ J ₃ > 3 FeSO ₄ {2}

Fe + H-SO ₄ ■ - > H- + FeSO. (3)

2 4 2 4.

It is known that the reaction (2) proceeds at about the same rate as the reaction (1), but the reaction is (3) considerably slower. Because of reactions (2) and (3) Actual iron consumption in cementation was usually in the range of 1.5-2.5 kg per kg recovered Copper.

It is known that the precipitation reaction is a reaction is of the first order and primarily from the replacement of exhausted solution in the boundary film surrounding the iron with fresh one Solution depends. Accordingly, multi-stage washing facilities are often used with a stoichiometric excess of scrap

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or waste iron in the form of tinplate cans, de-tinned waste materials, Turning chips, filings and the like are used. A typical way of working is to use the washing facilities a batch of scrap iron, the copper-containing one To direct the initial solution through the washing facilities until the iron is used up, and to empty the washing facilities then remove the precipitated copper. More recently, reactors have been used in which the solution has a high initial velocity and has a low top speed. In such reactors, the solution flows upward through an in A bed of iron located in an enclosed space to a larger, comparatively quiet zone. Such reactors can are in the shape of an inverted cone. In one case the iron does not form a bed but is dissolved in one Maintained state of dynamic suspension. In this embodiment, sponge iron is the preferred precipitant dar; however, the cost of sponge iron makes its usefulness in many places in question. In addition to washing devices and conical vessels, there are also cylindrical vessels with a horizontal shape or slightly inclined position of their axis and means for rotating the vessels, known. In such reactors the Ilisencharge is constantly being circulated and abrasion occurs one that is considered beneficial.

The cheapest suitable material is used as the starting iron at any given processing point. There are tin cans, cutting waste, turnings, Nails, coarse scrap, etc. are used (tin precipitates copper). The need to have cheap iron available poses arguably the only major obstacle to large-scale cementation application and the most serious problem in existing systems. In particular, the price of Schiot-t is subject to extremely strong fluctuations, and when the price will be high, the cementing will be economical not interesting. In addition, the quality of the traded

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Scrap unreliable. From processing plants, the The trap bar is often coated with fat or oil and these must be used removed. Painted surfaces are unusable because they do not react. Paper, rock or wood as well other metals are often present as accompanying substances. All of these impurities reduce the purity of the cement copper. Typically the product consists of 80-85% copper. Particularly important is also that the impurities in the iron itself cause difficulties, since impure iron, especially iron with a high carbon content, tends to precipitate very firmly adhering copper, which then causes the reaction Completely blocked in the absence of an accessible iron surface.

The physical size and shape of scrap or scrap iron also poses problems. The lack of one uniform reaction surface leads to "the * cementing process difficult to control, and incomplete copper recovery may result, the recycle treatments or other additional measures are necessary. In particular, it should be noted that when using the scrap or waste iron There is no control of the proportions of the reactants until exhaustion. Continue to have to Facilities and personnel for storage, shredding, cleaning ■ The movement and movement of the scrap or scrap iron can be provided. Large pieces of scrap or scrap iron naturally reduce the effective volume of a reactor.

Cement copper made by conventional techniques is generally in the form of a fine powder with a grain size in the range of 10-100 microns. Such a product oxidizes very quickly on contact with air to Cu-O, which further reduces the product purity. Such a thing unclean product must of course be refined to make it salable, and because of the small size Particle size are special precautions to avoid Dust losses necessary.

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The invention is based on the object of a cementing process to create that does not include the above and similar slopes! has known working methods and yet it can be carried out easily, safely and not prone to failure. In connection with this, the invention aims in particular the indication of a cementation process which is a Recovery of the metal in yields as high as 99.9% in the form of a product of higher purity than previously known Process allows a cementation product of high specificity Weight and larger particle size than previous processes, so that losses during refining are reduced works with a cheap, easily available and price-stable precipitant and also no cumbersome or special equipment to be manufactured. ,

Further advantages and preferred features emerge from the explanation below and the preferred ones specified Embodiments emerge.

In the attached drawings, Figures 1 to 7 show diagrams in which the available amount of precipitated copper, as a percentage against which time is plotted.

Figure 1 illustrates the influence of a change in the amount of precipitant present.

FIG. 2 illustrates the influence of a change in the amount of precipitant with increased stirring or agitation.

FIG. 3 illustrates the influence of a change in the copper content of the solution used.

Figure 4 illustrates the influence of changing the Speed of rotation of the reactor, i.e. the amount of movement.

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FIG. 5 essentially corresponds to FIG. 3, however for other operating conditions.

FIG. 6 corresponds essentially to FIG. 4, but for different operating conditions.

Figure 7 illustrates the influence of changing the Flow rate of the solution used.

The invention is explained below primarily with reference to the cementation of copper on iron, but it is not limited to this.

"It was found that impure iron granules in a continuous cementation process without blocking can be used by precipitated copper, provided the physical and kinetic conditions controlled within certain limits. Oils significant physical factors are the size, the shape and the surface of the precipitant, the type of reactor and its operating speed. The kinetic factors are the ones too surface area of the precipitant available for a given time, which is produced by the reactor per unit of time the flowing volume of the applied solution, and the concentration of copper in the solution. Other factors, e.g. pH and temperature, are also controlled, but their role is not as important as those given above Parameter.

Pig iron grains are preferably used as the precipitating agent, the preference being based primarily on their low costs and easy accessibility. The granules usually have a high carbon content and a variety of impurities are present; it is only necessary to avoid large amounts of such impurities that passivate the iron, that is, chromium and / or ¹ Nickel. Know the granu-

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Lat grains are formed by passing molten droplets through a horizontal jet of steam and water directs, they have irregular shape with a rough raisin-like surface, which is suitable for the purposes of the invention has proven particularly suitable. However, pig iron kernels produced by conventional shotting are also used with smooth surfaces quite satisfactory. It has been shown that - because the solutions used are acidic - the presence of an oxide layer on the surfaces of the grains is insignificant. However, both the size and The size distribution of the granules is also important.

In addition to creating a large surface area per unit of volume a certain particle size distribution supports the process of abrasion of the particles in strongly moving or stirred systems. It has previously been recognized that the reaction is faster with smaller precipitant particles expires; however, this only applies up to a certain point. It it has been found that larger particles are necessary to provide sufficient mass and small particles are necessary to to ensure sufficient density, so that a self-abrasive mass is formed. In this context is too Note that small-scale tests on a laboratory scale can give very misleading results, as small amounts of granulate are used of just a few kilograms result in very little abrasion and copper can build up on the surfaces, while in a reactor of technical scale with several thousand kilograms of granulate excellent abrasion is present and constantly fresh precipitation surfaces are generated. In previous investigations, stirring or movement of the solution to copper fractions Bringing through the boundary film to the iron surface has been particularly pointed out, but it is not sufficient Attention to the other side of the problem, which is the removal of copper from this surface. It has been found that a graded particle gerdsch,

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in which 50 to 80% a grain size determined by sieving of more than 1.65 mm (+10 mesh) is a very satisfactory precipitant.

Although pig iron grains because of their low cost and good accessibility, others can also be preferred Materials used: foundry iron, pearly steel, cast iron, cupola iron, and the like are all useful. It is only necessary to avoid impurities that passivate the iron or those under the reaction conditions contaminate the precipitate. A particle size and particle size distribution tailored to abrasion are much more important than the chemical composition.

A variety of reactors can be used in the process can be used, but the simplest is a cylindrical one Vessel that is arranged lying on pivot bearings for rotation at a regulated speed and has an inlet at one end and has an outlet at the other end. During the turning process, the precipitant is constantly poured into itself and circulated and the particles rub off each other. The rotation also creates the movement of the solution that induces it good contact between reactants is required. The abrasion and the movement will be both are improved if the vessel is equipped with lifting pieces, i.e. protruding parts on the inner wall parallel to the vessel axis. Radial lifting pieces on the outlet end wall facilitate the discharge of used solution, precipitation product and non-residue Precipitants. The latter can be separated magnetically. For reasons that will become apparent below comparatively short vessels of larger diameter are preferred over longer, thinner cylinders. The vessel can be arranged horizontally, but mostly it is slightly inclined so that the inlet is slightly higher than the outlet.

Although usually aimed at high production rates ■ • srden and for this movement and abrasion are necessary, can

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the method of the invention also in a washing facility or another dormant reactor. In order to avoid / that copper forms a firmly adhering coating, however, it is then necessary to use the value defined below Increase the response index very considerably, to at least about 10 or above. In other words, nut either the amount of precipitant must be greater or the concentration and / or the flow rate of the task- ^ solution can be reduced. In the case of very dilute solutions and a system that is equipped with washing facilities, for example is, such implementation of the method to be appropriate to the invention »

The concentration of the solution supplied, that is, the feed solution * - is generally specified and can be entered. economic aspects cannot be changed »The solutions can be very dilute, with 1 g / liter or less copper, or solutions with up to 30 g / l Cu. The quantities that can be changed are the rate of solution delivery, the total amount of precipitant present and, to a limited extent, the speed of rotation of the vessel. Of course, it is expedient to find the solution with the greatest possible Add throughput while still completely recovering the copper »

Previous workers have unanimously stated that: 3. had a stoichiometric excess of scrap or waste must be present for good results! door the measures to extract a few kilograms of iron per kilogram Providing copper, however, is insufficient and ineffective and can lead to the formation of a blocking, adhering copper layer. which terminates the reaction. The exceptionally beneficial results of the method of the invention are probably due to (1) presentation of the precipitation device in a form in which a comparatively high

309818/0077

The ratio of surface area to volume is given »and (2) performance an amount of precipitant, which is constantly with the several hundred to several thousand times the stoichiometric Amount is held at any given time to the complete exhaustion of the solution present is required. The constant abrasion of iron and Copper can be responsible for the high quality of the cement copper produced and its favorable density and particle size be viewed, surprisingly, is the iron consumption per kg of copper quite low, only about 1.1-1.2 kg. below optimal conditions.

The following equation can be used to calculate the ^{amount of precipitant to be added in the 1} method of "finding"? *

■■ <«>!

herein mean

P «weight of the precipitant, in kg c ** copper concentration, in g / l $» volume of the feed solution, in l / min I m reaction index.

It can be seen that this expression “ah!” Does not take into account factors such as the size of the precipitant, the pH value, the conditions with regard to agitation or stirring, etc. the preferred abrasion contact of the particles as well as the given operating conditions, a reaction range of 1 - 10 leads to very good results, with a range of 1 - 2.5 being preferred. As mentioned above, a higher reaction index was obtained for a system at rest. The extent of the st ^ chiovatric excess of precipitating agent required in a process of the invention. '<a.nn can easily be taken into account. It is the norm

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Application solution with 10 g / l Cu In a volume of 1000 l / min and a reaction index of 2. The solution of the equation (4) for the addition of precipitant results in 20,000 kg. The amount of precipitant present is thus about 2300 times the amount theoretically required at any given time to exhaust the solution present is. When carrying out the process, it is expedient to keep the reaction index as constant as possible; this means in the above example that 11-13 kg of fresh precipitant per minute are to be introduced into the reactor.

Overall, the process of the invention is therefore preferably carried out using pig iron grains with a high surface / volume ratio but for inducing self-abrasion of sufficient size and size distribution in a reactor which favors such abrasion, the amount of the precipitating agent present being several hundred to several thousand times the stoichiometric amount required at any given time. Under these conditions, a cerium with a higher copper content is produced. Copper recoveries of 99.9 % are achieved. Using the same equipment as heretofore used for cementing scrap or scrap iron, productivity could uir. 300 to '00% increased. The grain size and density of the copper produced are better. Facilities and personnel for comminuting, transporting and storing scrap above Abiaileisen are practically no longer required, since the granulate can easily be handled in automatic facilities. In addition, as already indicated, the iron consumption is surprisingly low. . - -

In carrying out the method, the Aufgabelösunc which is introduced into the reactor inlet, very quickly, almost -oir.entan _f from their Kupferqehalt released and the exhausted Icsung, to the reactor outlet for a certain amount of the flow

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Time required tends to be due to its acidic nature to solve Elsen (equation 3). For this reason, comparatively short reactors of larger diameter are preferred.

The invention is further illustrated below by way of examples, which, however, are illustrative Character and the invention is not limited to these particular embodiments.

Examples

In the studies listed below, two types of granulated pig iron were used as the precipitating agent. The first material, hereinafter referred to as Type A, had a smooth surface and roughly elliptical shape. the Grain size distribution was as follows:

well Grain size (Mesh) 1.65 (+ 1O) > 65 - 0.25 (-10 + 60) 1, «£ 0.25 (-60)

88.8 3.0 8.2

The chemical composition was as follows:

Total carbon 4 3

tied O, 6

graphitic 3.7

.Mn 0.72 j

P 0.14 ^!

3 O, O52

Si 0.65

Total Fe 80 J

tied 0 _Ί and minor con]

unclean!'? .rnqan remainder t

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Other impurities found were Ca, Mg, and others.

The second precipitant, hereinafter referred to as Type B, was similar in shape and surface finish Raisins. The grain size distribution was as follows:

Grain size
mm (mesh)%

> 1.65 (+10) 78.6

1.65 - 0.25 (-10 + 60) '19.9

210.25 (-60). 1.5

The chemical composition was as follows:

Total carbon 3.85 - * "

bound 3.68

graphitic °> ¹⁷

Mn O.06

P 0.28

Si 0.62

S 0.07

Total Fe 83.3.

bound O, and impurities remainder

The impurities included 0.4 % V, 0.1% Ti, Ca, etc. In this iron, about half of the bound carbon was cenentite. For the sake of interest. noted that large piles of this precipitant would be stored on the seashore for about a year and exposed to ambient conditions. The material was covered with a thin layer of oxide, but this was dissolved in the reactor in a few seconds. It is even more important that the heaps showed no appreciable tendency to cake or sag and the material was easy to handle.

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The examinations were initially carried out in a cylindrical Vessel 250 mm long and 290 mm in diameter carried out. The inlet was circular axial opening in one end of 12.5 mm diameter. The outlet comprised 36 holes in three rings in opposite directions End, the outer ring was 12.5mm in diameter. The vessel was slightly inclined towards the outlet and had a Working volume of 2.74 liters.

The vessel was mounted for rotation at rotational speeds up to 35 rpm (in such investigations in small Higher rotation speeds than are applicable in industrial-scale reactors tend to compensate for this the lower load rait precipitants). A pump was used to supply the solution in an amount

4. W *

up to 0.37 l / min. The results of these tests are summarized in Table I below.

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Table I.

-A- BCDE FQ) G , H ₁₁₁₁ , I

rie.ihfctortakennznhl. 0.48 0.95 0.50 1.07 1.43 1.43 1.26 1.91 "5.94

qxnulated raw material, type A A B B A A BB B

Copper extraction,% (1) (1) (2) '

29.6 97.7 88.6 97.6 99.6 99.8 95.9

Kupi; Grc] ohalt des Fiill- '. ■■■. .

Product,% (1) (1) 81.4 82.6 82.4 81.3 89.4 82.8 79.1

o Yield, kg precipitation,.

co medium / kg Cu ^v (1) (1) - 1.14 1.15 1.21 1.15 1.10 1.37

Ξ Duration of use, min 60 120 411 '330 270 375 1020 330 450

co. . ■. ■ ',. ■■. ■. ■■.

ο ■ ■. . . ■. ■. ■

σι (1) No copper was obtained. The copper adhered firmly to the precipitant and blocked

■ ^ the reaction. ; '':

■ ^y (2) Only the given one is used! low copper content obtained. In addition, the copper "; firmly covered the precipitant and blocked the reaction. This experiment was carried out at 18 O / mln. Experiments A and B were carried out at only 1 U / mln.

(3) In this experiment, the reaction index v / ie was the same as in experiment E, however this experiment was carried out at 6 rpm, while experiment E was carried out at 1 rpm.

= 2

cn ω

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From these investigations it can be concluded that the value of the reaction index should be at least 1 for both precipitants used. At lower values, the copper envelops the precipitant and blocks the reaction. The reaction index can be as high as 10 _r, however, for economic reasons the preferred range is 1 to about 2.5.

FIG. 1 shows that the copper recovery increased significantly when the amount of precipitant was increased from 1 to 4 kg, but it did not go beyond 90%. By increasing the speed of rotation and increasing the precipitant agent up to 20 kg, yields of over 96.5 % up to 99.5% were achieved, as shown in FIG. With a precipitant concentration of 25 kg, it was possible to maintain excellent yields at a high flow rate and higher copper concentrations, as shown in FIG. The influence of the speed of rotation and thus the movement is shown in FIG. 4; in large-scale implementation, however, as already mentioned, a comparatively low rotational speed (1-3 rpm) is expedient and satisfactory. \ i.fte much reinforced. Precipitant B, with its calm textured surface, was found to be more effective than Type A Precipitation Center 1, as can be seen from Figure 5, where slow agitation, high flow rate and concentrated solutions were used. A considerable improvement was achieved by increasing the speed of rotation from 1 to 6 rpm, as can be seen from FIG. At the lower rotational speed, good results were achieved with lower flow rates, as shown by FIG. 7.

In the course of these trials, other industrial roads were also investigated. Both industrial waste solutions were used. si «; L ^ iboratoriunslösung also used. Dar - * lh ^T ert

BAD QFUGlNAL 309818/0677 ^

was changed from 1.5 to 3.0 and the initial temperatures were changed between 10 and 80 ° C. It turned out that that the effects of these changes in your method of "" finding were not different from what was to be expected based on conventional "cementations".

There have also been trials on a semi-industrial scale carried out in which the precipitant of type E and a Vessel 3.4 m long and 1.15 m in diameter was used. During the examinations, a control was carried out for several weeks. and comparison vessel operated with scrap iron in the conventional manner using the same feed solutions. The vessel operated according to the method of the invention produced 3.5 times as much copper as the comparison vessel. Farther the copper content of the cement was higher and the iron consumption was lower. The results of these investigations are compiled in Table II below.

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Table II I - II - 2 T - 3 1 - 4 1-5 1-6 1-7

u ^ χ ^ nge, ^ _i5 ^ ^ ^ ₁₅ ^ _{40 lfl5 χ 3> 4O l # 15 χ 3/40 1 # 15 x 3} , _{4O 1 / l5 x} 3.40 2.20 κ 2

Au rs Ij β on the edge on the edge in the middle in the middle raittig in the middle in the middle

hUi) 3.5 - 0.8 1.3 - 2.1 1.5 - 1.9 3.0 - 3.3 1.1 -1.3 2.6 - 3.0 1.3 - 1,

y y im

_jus',. · fall ten copper, - ftO

© _: 85 - 65 86 - 88 87 - 90 84 - 86 89 - 93 84 - 86 86 - 89

% . «Wnnung, I 99.0 - 3.0» 9.5 ^, 99.6 99.7 99.7 99.7 99.5

φ Hrqieblgkcit, kg ■■■ '-'_ ■':

_{m kq} Cu 1.46 - 0.0 1.41, 1.35 1.50 1.30 1.39 1.12

m '- ' · '■■■ -. ■■ - ■ - ■

* (1) in experiment I -!. Was the flow rate, i.e. the liquid throughput,

increased to a level at which the response index fell below 1; deposited copper immediately blocked the reaction.

δ (2) These experiments were used to determine changes in the reaction parameters

§ number of fluids added at different intervals. It will be natural

borrowed preferred, the precipitation agent continuously or in regular intervals

^ a few minutes to add. ".

■ .--; _ 19 -

Using identical solutions.-in two essentials identical cylindrical precipitation vessels with a central outlet, as described for experiments 1-3 to 1-6 are, was made using fine scrap iron in one Vessel and granulated pig iron of type B precipitated copper in the other vessel. Fine scrap is considered particularly suitable viewed for the-cementation ... of copper. Both precipitation vessels were rotated at 3 rpm., -

The maximum generation obtained from the scrap was 1000 l / h of a copper sulfate feed solution containing 25 g / l. With this throughput volume, 95 to 97% of the copper recovered. The copper precipitate contained between 66 and 75% copper, and an average of 1.3 kg Precipitant consumed per kg of copper produced. . -

A comparison with the performance values that were achieved when carrying out the method according to the invention clearly shows essential technical advantages of the invention. According to the method of operation of the invention, 3500 l / h of the same above-mentioned feed solution could be processed throughout; the reaction index was kept between 1.05 and 1.20. Despite this increase in throughput and thus productivity to 350 % , the copper precipitate contained between 85 u ·? .Ί. S3% copper, the copper recovery was consistently higher than SS "[ i.e. the highest measured copper recovery was 99.85%), ur -? The average yield was 1.26 kg consumed Jo!., 'X"! cmeans per kg produced "'supplies. -

It can be seen that with regard to the materials, work-7.-c.ä! Iahir, €? N "and process equipment or other details, as explained above to illustrate the invention, changes or changes depending on the individual case - '.' 0 ^ dIu ^- IyOn vergenorrjr.er. Can be without the Ragnor, eier Erfiniun ^. ·: Ν vorIdpse--.. ·

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Claims (10)

Claims 1. Method of cementing metals by precipitation of the desired metal from an acidic salt solution to an electropositive precipitant, characterized in that that the precipitant is in the form of a graded mixture of particles with high surfaces / Volume ratio but of sufficient size, do '' under stirring or agitation conditions to ensure self-abrasion begins and the ratio of precipitants to the desired ones Metal constantly with the several hundred to several thousand mechanics the stoichiometric ratio required to precipitate the desired metal. 2. The method according to claim 1, characterized gekennzeichr.3t, That is, iron is used as the precipitant and the desired one Metal copper fails. 3. The method according to claim 2, characterized in that ran used as the precipitant pig iron, foundry iron, cast iron or nerlitic steel. 4. The method according to any one of claims 1-3 / characterized in that a mixture of as a precipitant Particles used, of which at least 50 to 80% one Have a grain size of more than 1.65 mm (+ 10 mesh). 5. The method according to any one of claims 1-4, characterized in that the particles are continuously in contact circulated with each other. ^ _nn ■ §AD ORIGINAL 3 0 9818/0677 6. The method according to any one of claims 1-5, characterized characterized in that the ratio of precipitant to the desired metal is constantly maintained by adding precipitant together with the salt solution. 7. The method according to any one of claims 1-6, characterized in that a koppers salt solution with a pH in the range of about 1.5 to 3 is used as the salt solution. :, 8. The method according to any one of claims 1 -. 7, thereby characterized in that one works under conditions without significant abrasion of the particles and the ratio of Keeps precipitant to the desired metal so high that the Formation of an adherent metal coating on the precipitant is changed. . ^. - 9. The method according to any one of claims 1-1, characterized in that a rotatable reaction vessel with pig iron grains with a grain size substantially greater than 1> 65 mm (+10 mesh) is charged as a precipitant, the salt solution is continuously fed to the reactor and consumed Solution and precipitated copper from the reactor. ..abzieht while de.r ,, _JReak.tgr: to. Upheaval, the. SisenkOrrier. rotated on itself with abrasion, while maintaining the ratio of iron precipitant to copper in solution in the reactor by substantially continuous addition of fresh precipitant to the reactor. 10. The method according to any one of claims 1-9, characterized characterized in that the ratio between the precipitant, in kg, and the desired metal, in g, determining the reaction number constantly between 1 and 10-stop. ':' 309818/0677